THE DIPTERA OR FLIES 49 



ranked as a distinct order, the Siphonaptera, which may 

 nevertheless have its closest relatives in the true flies. The 

 fleas resemble most flies in havng mouth parts adapted 

 for piercing and sucking, and their long and powerful 

 legs give them such effective powers of rapid movement 

 that wings would be almost superfluous. There are a 

 great many species of fleas infesting different species of 

 mammals and birds, but only a few attack man. The 

 eggs are laid in hairs or among the feathers of the host 

 and are usually shaken off. Hodge reports that "from 

 a lady's dress on which a kitten 

 had been fondled for a short 

 time, fully a teaspoonf ul of flea's 

 eggs were, collected." The 

 larvae are slender, whitish grubs 

 which feed upon dried animal 

 and vegetable matter. There 

 is a pupa stage of short dura- 



tion, the whole period from egg FIG. 40. Female of flea, 



to adult in the common cat and fj* r j^' infesting man " 



dog fleas being passed through in 

 not more than two weeks. Fleas, like mosquitoes, are dis- 

 ease carriers; one of the most dreaded diseases that afflicts 

 mankind, the plague, which has carried off its hundreds 

 of thousands in various epidemics that have swept over 

 Europe and Asia, is carried by fleas. The disease attacks 

 rats and squirrels as well as man, and wherever there 

 are infected animals there is constant danger of an out- 

 break among human beings. The fleas coming from rats 

 will readily carry the disease to man and from one man 

 to another. Consequently when the plague was intro- 

 duced into San Francisco a few years ago a crusade was 

 made against the rats. Chinatown was subjected to the 

 strictest search for these vermin and rats were trapped 



